Forget the minnows. Throw a jig.
If you are determined to use a minnow, the styrofoam buckets keep your minnows colder a lot longer than a plastic bucket. Add aeration and keep them fellars cold. Use ice if needed, but they have to stay cold.
Jigs don't have all that bother and when the Crappies are biting, you won't be wasting time with dead minnows in the summer.
old ship